[llvm] [CGP] Drop nneg flag when moving zext past instruction (PR #72103)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Mon Nov 13 03:15:23 PST 2023
https://github.com/nikic created https://github.com/llvm/llvm-project/pull/72103
Fix the issue by not reusing the zext at all. The code already handles creation of new zexts if more than one is needed. Always use that code-path instead of trying to reuse the old zext in some case. (Alternatively we could also drop poison-generating flags on the old zext, but it seems cleaner to not reuse it at all, especially if it's not always possible anyway.)
Fixes https://github.com/llvm/llvm-project/issues/72046.
>From c5e0710775114891058a7095abd859f5e0846183 Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Mon, 13 Nov 2023 12:08:47 +0100
Subject: [PATCH] [CGP] Drop nneg flag when moving zext past instruction
Fix the issue by not reusing the zext at all. The code already
handles creation of new zexts if more than one is needed. Always
use that code-path instead of trying to reuse the old zext in
some case. (Alternatively we could also drop poison-generating
flags on the old zext, but it seems cleaner to not reuse it at
all, especially if it's not always possible anyway.)
Fixes https://github.com/llvm/llvm-project/issues/72046.
---
llvm/lib/CodeGen/CodeGenPrepare.cpp | 38 ++++++-------------
.../CodeGenPrepare/X86/multi-extension.ll | 4 +-
.../Transforms/CodeGenPrepare/X86/pr72046.ll | 19 ++++++++++
.../CodeGenPrepare/X86/promoted-trunc-loc.ll | 2 +-
.../X86/promoted-zext-debugloc.ll | 2 +-
5 files changed, 35 insertions(+), 30 deletions(-)
create mode 100644 llvm/test/Transforms/CodeGenPrepare/X86/pr72046.ll
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index fa0c753bff2f073..07dc718ee3a38c3 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -4568,8 +4568,6 @@ Value *TypePromotionHelper::promoteOperandForOther(
// Step #2.
TPT.replaceAllUsesWith(Ext, ExtOpnd);
// Step #3.
- Instruction *ExtForOpnd = Ext;
-
LLVM_DEBUG(dbgs() << "Propagate Ext to operands\n");
for (int OpIdx = 0, EndOpIdx = ExtOpnd->getNumOperands(); OpIdx != EndOpIdx;
++OpIdx) {
@@ -4597,33 +4595,21 @@ Value *TypePromotionHelper::promoteOperandForOther(
}
// Otherwise we have to explicitly sign extend the operand.
- // Check if Ext was reused to extend an operand.
- if (!ExtForOpnd) {
- // If yes, create a new one.
- LLVM_DEBUG(dbgs() << "More operands to ext\n");
- Value *ValForExtOpnd = IsSExt ? TPT.createSExt(Ext, Opnd, Ext->getType())
- : TPT.createZExt(Ext, Opnd, Ext->getType());
- if (!isa<Instruction>(ValForExtOpnd)) {
- TPT.setOperand(ExtOpnd, OpIdx, ValForExtOpnd);
- continue;
- }
- ExtForOpnd = cast<Instruction>(ValForExtOpnd);
- }
+ Value *ValForExtOpnd = IsSExt
+ ? TPT.createSExt(ExtOpnd, Opnd, Ext->getType())
+ : TPT.createZExt(ExtOpnd, Opnd, Ext->getType());
+ TPT.setOperand(ExtOpnd, OpIdx, ValForExtOpnd);
+ Instruction *InstForExtOpnd = dyn_cast<Instruction>(ValForExtOpnd);
+ if (!InstForExtOpnd)
+ continue;
+
if (Exts)
- Exts->push_back(ExtForOpnd);
- TPT.setOperand(ExtForOpnd, 0, Opnd);
+ Exts->push_back(InstForExtOpnd);
- // Move the sign extension before the insertion point.
- TPT.moveBefore(ExtForOpnd, ExtOpnd);
- TPT.setOperand(ExtOpnd, OpIdx, ExtForOpnd);
- CreatedInstsCost += !TLI.isExtFree(ExtForOpnd);
- // If more sext are required, new instructions will have to be created.
- ExtForOpnd = nullptr;
- }
- if (ExtForOpnd == Ext) {
- LLVM_DEBUG(dbgs() << "Extension is useless now\n");
- TPT.eraseInstruction(Ext);
+ CreatedInstsCost += !TLI.isExtFree(InstForExtOpnd);
}
+ LLVM_DEBUG(dbgs() << "Extension is useless now\n");
+ TPT.eraseInstruction(Ext);
return ExtOpnd;
}
diff --git a/llvm/test/Transforms/CodeGenPrepare/X86/multi-extension.ll b/llvm/test/Transforms/CodeGenPrepare/X86/multi-extension.ll
index cc8e99176bf6e12..d09193e75f99742 100644
--- a/llvm/test/Transforms/CodeGenPrepare/X86/multi-extension.ll
+++ b/llvm/test/Transforms/CodeGenPrepare/X86/multi-extension.ll
@@ -10,8 +10,8 @@ declare void @bar(i64)
; %or is reachable by both a sext and zext that are going to be promoted.
; It ensures correct operation on PromotedInsts.
-; CHECK: %promoted = trunc i32 %or to i16
-; CHECK-NEXT: %c = sext i16 %promoted to i64
+; CHECK: %promoted3 = trunc i32 %or to i16
+; CHECK-NEXT: %c = sext i16 %promoted3 to i64
define i32 @foo(i16 %kkk) {
entry:
%t4 = load i16, ptr @b, align 2
diff --git a/llvm/test/Transforms/CodeGenPrepare/X86/pr72046.ll b/llvm/test/Transforms/CodeGenPrepare/X86/pr72046.ll
new file mode 100644
index 000000000000000..d75e5632ebb2e58
--- /dev/null
+++ b/llvm/test/Transforms/CodeGenPrepare/X86/pr72046.ll
@@ -0,0 +1,19 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
+; RUN: opt -S -codegenprepare -mtriple=x86_64-unknown-unknown < %s | FileCheck %s
+
+; Make sure the nneg flag is dropped when lshr and zext are interchanged.
+define i8 @get(ptr %box, i32 %in) {
+; CHECK-LABEL: define i8 @get(
+; CHECK-SAME: ptr [[BOX:%.*]], i32 [[IN:%.*]]) {
+; CHECK-NEXT: [[PROMOTED:%.*]] = zext i32 [[IN]] to i64
+; CHECK-NEXT: [[SHR:%.*]] = lshr i64 [[PROMOTED]], 24
+; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr inbounds i8, ptr [[BOX]], i64 [[SHR]]
+; CHECK-NEXT: [[RES:%.*]] = load i8, ptr [[ARRAYIDX]], align 1
+; CHECK-NEXT: ret i8 [[RES]]
+;
+ %shr = lshr i32 %in, 24
+ %idxprom = zext nneg i32 %shr to i64
+ %arrayidx = getelementptr inbounds i8, ptr %box, i64 %idxprom
+ %res = load i8, ptr %arrayidx, align 1
+ ret i8 %res
+}
diff --git a/llvm/test/Transforms/CodeGenPrepare/X86/promoted-trunc-loc.ll b/llvm/test/Transforms/CodeGenPrepare/X86/promoted-trunc-loc.ll
index 081c6742ede8c91..0ff35e1406de2bf 100644
--- a/llvm/test/Transforms/CodeGenPrepare/X86/promoted-trunc-loc.ll
+++ b/llvm/test/Transforms/CodeGenPrepare/X86/promoted-trunc-loc.ll
@@ -1,7 +1,7 @@
; RUN: opt < %s -codegenprepare -S -mtriple=x86_64-unknown-unknown | FileCheck %s --match-full-lines
; Make sure the promoted trunc doesn't get a debug location associated.
-; CHECK: %promoted = trunc i32 %or to i16
+; CHECK: %promoted3 = trunc i32 %or to i16
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.13.0"
diff --git a/llvm/test/Transforms/CodeGenPrepare/X86/promoted-zext-debugloc.ll b/llvm/test/Transforms/CodeGenPrepare/X86/promoted-zext-debugloc.ll
index 0b4f830ff3e7d99..f293d46ed6f74c6 100644
--- a/llvm/test/Transforms/CodeGenPrepare/X86/promoted-zext-debugloc.ll
+++ b/llvm/test/Transforms/CodeGenPrepare/X86/promoted-zext-debugloc.ll
@@ -1,7 +1,7 @@
; RUN: opt < %s -codegenprepare -S -mtriple=x86_64-unknown-unknown | FileCheck %s --match-full-lines
; Make sure the promoted zext doesn't get a debug location associated.
-; CHECK: %promoted = zext i8 %t to i64
+; CHECK: %promoted1 = zext i8 %t to i64
define void @patatino(ptr %p, ptr %q, i32 %b, ptr %addr) !dbg !6 {
entry:
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